Slip-on, sheet-metal, nuts are used to connect supports such as, for instance, motor vehicle body sheet metal with other parts. Such nuts usually have a centering strip for allowing preassembling of the sheet-metal nut on the support before the assembly proper and requiring no special holding during the subsequent fastening of the screw, whereby assembly is greatly facilitated especially where the fastening holes are inaccessible, except by the screw.
In conventional slip-on nuts, the centering strip is usually stamped out only across approximately three-quarters of the circumference of the circular passageway in the planar or, so-called, lower leg of the nut. The centering strip is stamped through from the outside surface of the nut to place the strip between the two legs of the nut. Rough edges are thus created which not only prevent the strip from returning into the plane of the lower leg, from which it was stamped, under the inherent elasticity of the strip, but also tend to scratch the support onto which the nut is fitted. Thus, both the strip and the edges of the nut in the lower leg around the strip tend to mar the surface of the inserted support.
If the support is sheet metal plate coated with only one protective layer, for instance a layer of enamel, then this layer must not be damaged by the assembly procedure. When the conventional nut is fitted on the support, however, the result is that the usually sharp edges of the centering strip scrape over the layer of enamel, because of the clamping force of the upper and lower legs, so that the metal surface at these fastening points is scratched bare and rusting is encouraged.